MTFCA Forum

As the title says. I have found a 23-27 Chevy 171cui whole motor for sale locally. Actually it's almost too nice. Grimy but turns over, has trans with it too only thing that appears to be missing is carb and the pushrods on the side and even they may be around. Price for the whole thing is $250. I checked it out today and the head seems very nice and nothing appears stuck or toast. Being pre 28 it is only two intaking ports and one big exhausting port. I was told it came out of a truck. I'd probably gut the motor for its crank, rods, trans maybe and of course the head. I'm wondering if a single port Chevy head is worth the effort of doing up with an adapter plate to a T block though. I'd probably go 6:1 or 6.5:1 on compression, put on a Zenith HP5A carb I have and run a big bore pipe exhaust with no muffler to help with back pressure.
Has anyone bothered to try a single port Chevy head? I know the 28 is more desirable with the two port exhaust but this is close and cheap. I asked a couple guys in our club locally and they agree it won't be as nice as the two port but overall performance we're not sure of. So I'm looking for anyone here that has personally tried a single port or knows of someone who has.

Can't help you on performance but first thing to check with those single port Chev heads is the top of the exhaust port for cracks, they can be bad and not worth trying to repair.

Single ports just in my opinion will not give much more performance than a high compression flat head with a good cam. A lot of work, not a lot of benefit. 1 to 1 ratio rockers, restricted exhaust port, etc. The 1928 with 1 to 1.333 ration rockers, Siamese ports in and out.., you will notice some serious torque and horsepower.

Just Saying,

Hank

Hey Matt, Dave down here in north Adams. I know this is more money but it’s Craigslist and I’m sure can be talk down. I know the allure of an ohv t engine! https://worcester.craigslist.org/pts/d/ ... 37771.html If the link doesn’t work let me know on Instagram

Not worth using the single port- they are prone to cracking! I have a spare '28 head if you're interested

The initial outlay may be cheap, but the rest of the project will be just as expensive, with little benefit. Look at it this way. It will cost heaps of dollars to restore a Cord Convertible. If you spend a heap an 6 cylinder car, it would be a nice car. Spend the same heap on a V8 model and your car will be worth a lot more. Spend that same heap on a supercharged V8 and you will be even better off.

Allan from down under.

I'd say go for it.

Not everything in life has to be about dollars consumed. Sometimes, what you learn could end up priceless in the long run.

Find a two port head. They are out there.

There is a saying about those single port heads -- there are thems that are cracked, and thems that will be.

Always wondered what was wrong with Chevrolet Metalurallagy... cracked heads, broken axles... you would think a company with such a huge racing history wouldn't have those kinds of problems... unless they were going SO cheap to go against Ford they were cutting corners right and left.

Everyone I know with an early bowtie sedan or touring (and I've known a few) has a spare rear axle on the floor of the back seat. That's more than just a chance breakage - it seems to be pretty universal.

Mmmm Susanne, I'll post a little story, I had 3x 4cly Chevs and 2x 6 clys pre going toT's. never broke anything on them and then I got my first T and was told, carry a spare axle, they break, Now I have 5 T's and never broke an axle, but a drum and crank, yes.

I made my own adapter plate (with a drill press and die grinder), bought the water outlet connection from Gene, had valve guides installed,a couple of seats, new valves and had both side of the plate and head surfaced. Most of my expense was my time figuring things out. I still came in WAY under what the low end over head setup would have been and on top of that learned a lot along the way! The only reason it is off the car is because I was having valve sticking issues (found out the pads on the rocker arms were the issue). Before I took it off I was running with coils, made a bracket like the 26/27 boxes. I think there have been a lot of the single port exhaust heads put on, (didn't RAJO or Frontenac have them too?) I too would suggest the two exhaust port head. Oh to add to this, I was not going for power (ok a little more does not hurt ) but more as I needed to do the whole project and get it done because it was just plain cool and fun.

Mark's response is exactly what I meant when I made mine. Thanks for the wonderful explanation of why you did it.

Question though- the adapter plate- does the thickness affect the compression ratio? I've always wondered how that worked raising the head up that amount.

TIA,

jk

Listen to Hank Lee. If anyone in the club or on the Forum knows these heads, its Hank.

Jason, the answer is yes. The Chevrolet head has NO combustion chamber in it. It is just flat. Consequently the entire combustion chamber is within the thickness of the adapter plate. Most I have seen are about 1", but it would be worth doing some calculations on volume to determine compression ratios before you commit to a certain thickness for the adapter plate.

As long as you allow room for the pistons to pop up and space for the valves to open, leave a lot that can be gained in compression depending on how it is designed.

Thanks for all of the responses guys. Mark Chaffin ended up.putting a 2 port for sale shortly after this and I bought it! Now I need an adapter plate, is Gene still making them?

Gene French post here and in the classifieds. He makes the babbitt boring outfits. If he does not see this send him a PM. He was working with someone else that was making them.